1. Field of the Invention
The present invention relates to a tire mold for cure molding a tire, a manufacturing method of a pneumatic tire by using the tire mold, and a pneumatic tire.
2. Description of the Related Art
In cure molding of a tire, a tread surface and a side surface of an uncured tire are pressed to a tire molding surface of a tire mold, and a heating operation and a pressurizing operation are applied to the uncured tire. At this time, if an air lying between the tire molding surface and the tire creates an air accumulation without being appropriately discharged, a notch-like recess is formed on an outer surface of the tire due to the air accumulation. The recess is recognized as an area which is peeled or depressed along a tire circumferential direction, and is particularly significantly created in the side surface.
Generally, a vent hole serving as an exhaust hole is provided in an area of the tire molding surface which comes into contact with the side surface of the tire. However, if a lot of vent holes are arranged, the number of rubber projections called as spews is increased in correspondence to the vent holes, and there is a risk that an outer appearance of the tire is damaged by cut traces of the spews. Accordingly, it is not practical to increase the number of the vent holes for a countermeasure of the air accumulation.
On the contrary, as shown in FIG. 10, there can be thought a structure in which groove-like saw cuts 51 are provided in an area 50 of a tire molding surface which comes into contact with a side surface of a tire, and the saw cuts are used as a flow channel for the air so as to enhance an exhaust efficiency. FIG. 10 shows an example in which the saw cuts 51 extending in a tire diametrical direction are arranged in a tire circumferential direction CD, and FIG. 11 shows an example in which saw cuts 52 inclined in relation to a tire diametrical direction, and saw cuts 53 intersecting the saw cuts 52 are arranged. However, there is a case that the air accumulation is still created, and it is known that there is room for improvement.
According to the knowledge of the inventor of the present invention, it has been known that the rubber flows into the area 50 of the tire molding surface from both an outside direction and an inside direction in the tire diametrical direction, and the air accumulation tends to be created at a confluence position thereof. Particularly, in FIG. 10, the rubber tends to flow in the tire diametrical direction, and the air accumulation accordingly tends to be created. Further, in FIG. 11, although the rubber flowing direction is dispersed, the saw cut pattern is uniform and a rubber motion flow is uniform. Therefore, there has been a case that the air accumulation is still formed at the confluence position.
Each of Patent Documents 1-5 describes a tire which is provided with projection-like ridges on a side surface, and it is assumed that saw cuts corresponding to the respective ridges are provided on a tire molding surface of a tire mold for cure molding the tire. However, the tire molds do not suggest any means for solving the creation of the air accumulation mentioned above.